698 CREATIVE CHEMISTRY ethyl lead was about 50 in 1916, while today unleaded gasolines with octane numbers as high as 80 are being marketed. One of the newer developments in petroleum technology is to treat straight-run gasoline in a hydro-forming plant to improve its octane rating. This process is halfway between hydrogenation and catalytic cracking. The cracking processes previously referred to have been used for many years to convert heavy petroleum products into gasoline by thermal treatment at temperatures in the range of 900-1100° F. at pressures usually above 100 pounds and frequently as high as 1000 pounds. Catalytic cracking processes have only recently been in commercial use. These processes produce gasolines of higher antiknock value and have other commercial advantages. One such process is that developed by Eugene Houdry, which uses an alumina-silica catalyst at a temperature of around 900° F. and a pressure slightly above atmospheric. The gasolines produced have an octane number of around 80, compared with 70 octane number for thermally cracked gasolines, and are low in gum and sulfur content. Catalytic cracking processes usually give higher total liquid yields than do thermal cracking processes. In 1941 another cracking process, known as the fluid catalyst process, promised still greater economy in production costs and higher yields. The gasoline content of crude oil varies widely with the origin of the crude, but the average is about 30 per cent or less. If it were not for the development of cracking processes, we would have consumed more than twice as much crude oil, and there is no way of telling what the price would have been today. Undoubtedly the research work which led to the cracking processes has been the most constructive conservation project up to the present time, because it has not only given us more than twice as much gasoline from a given amount of crude oil, but it has also practically doubled the efficiency of automobile engines because of the higher compression ratio which the higher octane number of cracked gasoline made possible. Tetraethyl lead used in gasoline in quantities of less than 0.1 per cent to improve the antiknock properties exceeds in dollar sales that of any other synthetic organic chemical with the possible exception of ethyl alcohol. Antioxidants, such as various substituted aminophenols, employed in concentrations of less than 0.01 per cent, stabilize gasoline against gum formation and deterioration during storage. Various kinds of synthetic organic chemicals, such as alkyl and axy\
"BETTER THINGS" FROM PETROLEUM 699 phosphates and phosphites, and metallic soaps, are added to oils to improve their lubricating properties. New fuels of the order of 100 octane number are obtained by treating butane and butylenes produced in large quantities from cracking operations. For example, isobutylene may be polymerized with sulfuric acid or a solid catalyst and the resulting compound hydrogenated to produce branched octanes of high antiknock value. Copolymers of the lower olefins are also produced in large quantities. In 1940, about 1,600,000 gallons of such polymer gasolines were made daily in the United States, of which some 600,000 gallons had in the neighborhood of 97 clear octane number, making them suitable for the manufacture of high-grade aviation fuel. An even more recent development is alkylation, which consists of reacting a lower isoparaffin — e.g., isobutane — with lower olefins — e.g., butylenes — in the presence of strong sulfuric acid to give just about the theoretical amount of combination product with an octane number in the range of 92-96 and a preponderance of material boiling in the aviation-fuel range. The newer airplanes in the United States, with engines having a compression ratio of eleven to one designed for 100 octane fuel, can lift 25 per cent more dead weight and gain 25 per cent more translational speed than airplanes with engines designed to use 87 octane fuel. Miles per gallon of gasoline for automobiles have not increased as much as one would expect during the past few years because the public has demanded higher and higher performance, i.e., more power to provide greater accelerating capacity and hill-climbing ability. Performance has been greatly increased during the past few years without any loss of miles per gallon of gasoline as the result of the use of gasolines of higher octane numbers and better volatility. Performance has been boosted since 1927 by an average of about 45 per cent, while the economy of operation has increased by almost 20 per cent. The next step in the improvement of the automobile will undoubtedly be that of higher fuel economy made possible by an increase in octane number. Experimental data show that an increase in octane number from 70 to 100 would make possible automobile engines with higher compression ratios that should result in a gain of about 28 per cent in both economy and performance at 60 miles per hour. In general an altogether knock-free fuel would make it possible either to double the mileage or to double the power, but not both at once. The use of higher octane fuels even if they are sold at higher prices would cost less than the use of present fuels, and at the same time a considerable conservation of our fuel resources would be made possible.